The invention relates generally to the field of propulsion systems. In particular, the invention concerns an on-board fuel cell system for mobile vehicles such as trains, marine vessels, automobiles and other mobile means of transportation.
As concerns surrounding traditional power sources persist, investigation into alternative means of power generation are becoming increasingly important. In particular, environmental and political concerns associated with combustion-based energy systems cannot be ignored. In an effort to reduce dependence on these types of power supplies and methods, interest is increasing in devices capable of generating electricity by consuming fuels without requiring combustion.
In addition to being utilized for the generation of electricity, however, combustion processes are most commonly used to power means of transportation such automobiles, trains, or marine vessels. Motor vehicles alone are among the chief contributors to pollution problems associated with combustion of fuel. So, while alternative power sources such as nuclear and hydroelectric systems may be suitable for large scale electric utilities, they do not present an ideal solution to the problems associated with powering means of transportation such as motor vehicles.
Alternatives to internal combustion engine powered motor vehicles have included various types of electric vehicles. Electric vehicles are well known in the art. Typical electric vehicles are powered by nickel-cadmium batteries which drive electric motors of anywhere from twenty to 100 horsepower. The batteries are generally rechargeable by stationary direct current (dc) power supplies. A problem with known systems, however, is that they require constant recharging and offer limited range between required recharging stops.
Known systems are also expensive. Solar rechargeable systems, such as are available from Solectria of Arlington, Mass., represent one attempt to increase the travel range and control the cost of electric motor vehicles. Drawbacks associated with the solar generation of electricity, however, include its usefulness being limited to clear weather and daylight hours, and the expense of the vehicle.
Fuel cells, therefore, have been explored as a means for powering electric vehicles and reducing the constant need to recharge the vehicle from off-board sources. Fuel cells electrochemically convert fuel, such as hydrocarbon fuel, to electricity. Typically, a combustion reaction is not involved.
A drawback associated with prior art fuel cell systems, however, is that they are not economically viable for applications in which the power rating of the fuel cell must meet propulsion demands. In motor vehicle applications, for example, a fuel cell system designed to provide sufficient power required by the vehicle for cruising, let alone for peak surge, would be prohibitively expensive. While various known systems have attempted to exploit the advantages of designating a surge battery to meet peak demand in motor vehicle applications, none has satisfactorily overcome the economic problems.
It is an object of the invention, therefore, to provide a system for powering a motor vehicle which does not require a combustion reaction.
It is another object of the invention to provide such a system which has a range comparable with that of traditional combustion engines without requiring interruptive recharging from off-board sources.
It is still another object of the invention to provide an economically feasible system for powering a motor vehicle which can accommodate typical motor vehicle surge and range demands.
It is yet another object of the invention to provide a fuel-cell powered vehicle that is capable of generating power for off-board consumption.
Other general and more specific objects of the invention will in part be obvious and will in part appear from the drawings and description which follow.
The present invention relates to a power supply system that enhances the economic viability of certain means of transportation that incorporate fuel cells to generate electricity. Such means of transportation are referred to herein as mobile vehicle fuel cell power systems, where vehicle, as used herein, refers to all means of transportation, for example, automobiles, trucks, trains, marine vessels, airplanes and spacecraft. For example, the power supply system of the present invention provides for the off-board use of the electric power generated by the on-board fuel cell of a mobile vehicle fuel cell power system such as an electric car. Off-board use, or use remote from the vehicle, of the electrical power can include delivery of power to a remote site, such as a local residence, for example, the residence of the owner of the vehicle, or to a local utility power grid, or to another mobile vehicle.
Off-board stations are provided for delivery of fuel to the vehicle and for receiving the electrical power generated by the fuel cell. The off-board station and the vehicle are appropriately equipped for quick and easy interconnection such that electrical power is drawn from the fuel cell for off-board use. In addition, the off-board station can be equipped to deliver fuel to the vehicle, with similar provisions for the quick interconnection of the vehicle and the off-board station. Vehicles can be considered mobile fuel cell systems that deliver power for off-board use when power from the fuel cells is not required for on-board uses, such as propelling the vehicle. Fuel cells may be incorporated into mobile vehicles in a number of ways. For example, fuel cells can be used in tandem with a gas turbine to propel a vehicle, such as a marine vessel or a train.
Note that the on-board use of the fuel cell need not be limited to, or even involve, propelling the vehicle or vessel. For example, fuel cells can be used to provide heating, ventilation and air conditioning (HVAC) systems.
According to other examples, a marine vessel can use an on-board fuel cell for on-board HVAC and for the provision of on-board electrical power; off-board uses can include the delivery of electrical power to an off-board station when the vessel is in port.
According to another aspect, the invention can employ from one to many off-board stations. For example, the owner or principal user of an electric vehicle can have an off-board station located near a primary residence. Alternatively, off-board stations can be provided at locations where electric vehicles are typically parked for an extended period of time, such as homes, shopping malls, parking lots and places of employment. The off-board station is can be electrically connected through power cables to a utility grid, to transmit a portion of the electrical power produced by the on-board fuel cell to a remote site for use. Conductive power cables, however, are not the only means for the high efficiency transmission of electrical power; such transmission has been demonstrated over free space using microwaves. Whatever the means of power transmission, the dual use of the vehicle fuel cell power plants, that is, use wherein the fuel cell supplies power for both on-board and off-board purposes, is intended to enhance the economic viability of mobile vehicle fuel cell power systems, promote the use of alternative power sources, and realize the attendant environmental benefits.
In another aspect, the invention comprises a power supply system for converting fuel to electricity, where the power supply system includes a mobile vehicle fuel cell power system and an off-board station. The mobile vehicle fuel cell power system further includes a rechargeable battery; a fuel cell for converting fuel to electricity and for recharging the battery; optionally a fuel supply for storing and providing fuel to the fuel cell; and apparatus for electrical connection to the off-board station for delivering to the off-board station the electricity generated by the fuel cell. The mobile vehicle fuel cell power system can also include apparatus for receiving fuel from the off-board station.
The off-board station typically includes apparatus for receiving electrical power from the mobile vehicle fuel cell power system and output apparatus for providing at least a portion of the electrical power for use off-board of the mobile vehicle fuel cell power system. The receiving apparatus can include, but need not necessarily include, electrical cables and/or receptacles for mating with cables. Output apparatus can, but need not necessarily include, a relay and/or a switch for electrical connection to an off-board site. A simple off-board station can comprise, for example, a receptacle, for electrically coupling with a cable connected to the mobile vehicle, and some electrical wiring attached to the receptacle for transmitting electrical power for off-board use. The off-board station can also include apparatus for delivering fuel to the mobile vehicle fuel cell power system.
In one instance, the fuel supplied by the off-board station and received by the mobile vehicle fuel cell is a hydrogen-containing fuel. However, the fuel can be a hydrocarbon fuel, in which case a fuel reformer, and perhaps a fuel shifter, are included on-board the vehicle for producing a hydrogen-containing fuel. Alternatively, a fuel reformer, and perhaps a fuel shifter, are part of the off-board station. In the latter case the off-board station can include a fuel storage tank for storing reformed fuel. Furthermore, hydrocarbon fuels often contain sulfur. Sulfur in significant quantities causes corrosion of the fuel cell and can destroy certain catalysts of the reformer and the fuel cell electrodes, as well as contributes to air pollution and acid rain when discharged into the air. Accordingly, a desulfurization unit can be incorporated in the present invention to remove sulfur prior from the fuel prior to the delivery of the fuel to the reformer. The desulfurization unit can form part of, according to one aspect, the off-board station, or the mobile vehicle fuel cell power unit.
Reactants for aiding the fuel reformation process are known in the art. Accordingly, in another feature of the invention, a reactant such as water is supplied to the reformer, whether located on-board the vehicle or at the off-board station, to aid in the reformation process. If the reformer is on-board, appropriate means are employed for supplying water to the vehicle. For example, water is supplied to the off-board station, and appropriate ports are provided at the station and on the vehicle, to accommodate a quick-connect hose connected therebetween. The power system of the present invention can include apparatus to filter and/or de-ionize the water, if such treatment is necessary. Note, however, that a reformer can be designed to simply utilize an oxidizer (e.g. air) instead of a reactant such as water. Use of a reformer, either on-board of off-board, need not require incorporation of means to deliver a reactant such as water to the reformer.
According to another aspect of the invention, meters are incorporated into the power supply system for metering, for example, the fuel received by the electric vehicle from the off-board station. Similarly, an electric meter can be also be used to measure the electrical energy or power delivered from the vehicle to the off-board site or from the off-board site to another location, e.g. the power grid or a local residence, for use remote to the vehicle.
A typical fuel cell produces direct current electrical power; a typical residence or utility power grid employs alternating-current electrical power. Accordingly, in one aspect of the invention, the off-board station includes an inverter or inverters for converting the direct-current electrical energy produced by the vehicle fuel cell to single-phase or multi-phase electrical power. A typical utility power grid transmits three-phase electrical power, and thus an off-board station, if supplying power to the grid, converts fuel cell electric power to three-phase alternating current. Alternatively, the inverter or inverters can be located on the mobile vehicle fuel cell power system to provide alternating current for off-board and/or off-board use. For example, if the mobile vehicle fuel cell power system is a train or a supertanker, the inverters can be located thereon. Of course, if direct current is desired for use remote to the vehicle, the off-board station need not employ an inverter for converting direct-current to alternating-current. The type of electric power meter employed in the power system depends on whether direct current or alternating current power is to be measured.
In yet another aspect, the off-board station includes a two-way or one-way telecommunications link to report condition parameters of the station, and perhaps of the electric vehicle, to another location. Condition parameters can include, but are not limited to, the quantity of fuel delivered to a vehicle, the amount of electricity supplied by the fuel cell of the vehicle for use remote to the vehicle, the identity of the vehicle or of the owner of the vehicle, and other usable parameters. The communications link can also transmit to the off-board station and/or the vehicle instructions for execution.
Many types of fuel cells are known to those of ordinary skill in the art to be useful in with electric vehicles. Accordingly, it is deemed within the scope of the invention to use several types of fuel cells, including but not limited to, solid oxide fuel cells, molten carbonate fuel cells, phosphoric acid fuel cells, alkaline fuel cells, and proton exchange membrane fuel cells.
The power system of the present invention envisions the off-board use of electrical power generated on-board the mobile vehicle fuel cell power system via the interconnection of the mobile vehicle fuel cell power system with an off-board station. However, the practice of the invention need not involve the use of an off-board station exactly in the manner described above. For example, a mobile vehicle fuel cell power system may be electrically connected to a second mobile vehicle electrical power system, such as another electrical vehicle, to recharge the batteries of the other vehicle. In this instance, the vehicle whose batteries are being recharged serves as a type of off-board station. The vehicles are appropriately equipped for quick and convenient interconnection. Both can include apparatus, such as male electrical receptacles, for coupling with the female connectors of a power cable connected between the fuel cell mobile vehicle power system and the second mobile power system for transferring electrical power therebetween. As both vehicles operate on dc power, an inverter is not always necessary. Note that the second mobile power system can be a fuel cell vehicle or a conventional (e.g., non-fuel cell) electric vehicle.
According to another aspect, the power system of the present invention is also deemed to include vehicles that do not employ fuel cells. For example, a mobile vehicle power system according to the teachings of the present invention can use traditional power plants, such as a combustion engine, an electrical generator, a battery, steam or gas turbines or generators and other power forms, such as solar power. The generator converts the mechanical energy of the combustion engine to electrical energy for on-board use, off-board use, and/or for storage by the battery. When the vehicle is coupled to an off-board station, the power plant delivers electricity to the off-board station for use off-board the vehicle and optionally receives fuel from the off-board station. The combustion engine can be an internal combustion engine, for example a diesel or gasoline engine, or an external combustion engine, such as a steam engine or a stirling engine. The mobile vehicle power system can include an electric motor for propelling the vehicle, as is typical in a diesel-electric train engine, or the combustion engine may propel the vehicle directly, as is typical in conventional automobiles.
Other general and more specific objects of the invention will in part be obvious and will in part be evident from the drawings and description which follow.